D.C. Public Schools Chancellor Antwan Wilson, appointed last year with a mandate to close a persistent student achievement gap, was forced to resign Tuesday amid revelations he skirted the city’s competitive lottery system so his daughter could transfer to a high-performing school.

The end of Wilson’s one-year, 19-day tenure — announced at a late afternoon news conference by Mayor Muriel E. Bowser (D) — sends another jolt through a beleaguered school system already engulfed in a graduation scandal. He was the second casualty of a crisis that emerged Friday with little warning: Deputy Mayor for Education Jennifer Niles was the first to go.

It was a stunningly swift fall for an educator hailed as the heir to the school reform agenda crafted by Michelle Rhee and her successor, Kaya Henderson. And it means that two key positions sit vacant in a school district roiled by turmoil.

Amanda Alexander, the school system’s chief of elementary schools, was named interim chancellor. She served as a deputy chief of schools under Henderson.

The chancellor’s departure delivers a political blow to Bowser, whose selection of Wilson, an outsider, was one of the most important and high-profile appointments of her tenure. Bowser is up for reelection this year, though she faces no credible challengers so far.

“There are too many tough decisions in the coming months to have any distractions,” Bowser said at the news conference. “I want to focus on finishing the year for our kids. I am obviously very disappointed, but I am committed.”

On Friday, Bowser said she remained confident in Wilson’s leadership and ordered him to publicly apologize. But by Tuesday morning, a majority of the 13 D.C. Council members had demanded Wilson’s ouster, and pressure grew for the mayor to remove him.

A spokeswoman for D.C. Public Schools referred questions to the mayor’s office. Wilson was not at the mayor’s news conference and could not be reached.

According to Wilson’s contract, Bowser can terminate the chancellor’s employment without cause. The contract — carrying a $280,000 annual base salary, a $14,000 signing fee and the possibility of a 10 percent performance bonus — was set to expire in January 2019.

Bowser said the terms of Wilson’s severance are being negotiated.

The mayor recruited Wilson, 45, from Oakland, Calif., to replace Henderson, who presided over D.C. schools for more than five years. When tapping Wilson, Bowser hailed him as a “proven manager” who could build on the changes of his high-profile predecessors.

As more educated families moved into the District and enrollment grew, Bowser hoped the new chancellor could close the stubborn achievement gap between children living in the city’s poorest neighborhoods and those in the most affluent.

Wilson’s year started quietly, and he largely maintained the status quo established by his predecessors. But last month, a city-commissioned investigation discovered that 1 in 3 graduates in 2017 missed too many classes or improperly took makeup classes, undermining the validity of hundreds of diplomas.

The seeds of the graduation scandal were planted before Wilson’s arrival, but the chancellor assured the public he could shepherd the school system through the difficulties.

But with the latest controversy — a scandal of the chancellor’s own making — parents and politicians said Wilson had forfeited the public’s trust. The chancellor had overhauled lottery system rules months before he broke them so his daughter could transfer to a different high school.

Bowser said she absorbed feedback from parents and education leaders over the weekend and realized the chancellor could not regain the public’s trust. She said that the graduation controversy played no role in her decision to remove Wilson and that she still believes the school system has made progress over the past decade.

“Stability and continuity in our system is very important, but in order for that to be effective, a leader has to have the trust of the people he manages and the people he leads,” Bowser said. “Let me say this: Chancellor Wilson is an extraordinary educator. He has built a career on helping students and transforming schools, and he is a human being that made a mistake.”

Patricia McGuire, president of Trinity Washington University and co-chair of a community committee in 2016 that helped select the chancellor, said the upheaval comes at an inopportune time for the school district.

“What a mess we are in, and to have leadership fail us so badly at such a critical time is unbelievable,” McGuire said. “This was a self-inflicted wound. This was a needless, needless, stupid thing to happen.”

Wilson started in the D.C. post last February, while his wife and three children finished the academic year on the West Coast before moving to the District last summer. Wilson participated in the lottery process to find schools for his children, and his oldest enrolled in the Duke Ellington School of the Arts in the fall as a sophomore.

A few weeks into the academic year, the family decided the arts magnet school was a poor match for the teen, and Wilson approached Niles, the deputy mayor. Wilson, knowing that strict rules govern school placement, had his wife speak to and coordinate with Niles. His daughter was transferred to Wilson High, a high-performing neighborhood school in Northwest D.C. with a wait list of more than 600 students.

Wilson’s neighborhood school is Dunbar High, a lower-performing school in Northwest D.C.

The citywide lottery system allows families who are unhappy with their neighborhood schools to win seats at different D.C. public schools or charter schools, if there is excess capacity there. But demand is great for the best-performing schools, where hundreds of families might compete for a handful of seats.

The famously competitive lottery system has been a long-standing source of tension and was mired in scandal less than a year ago when investigators discovered that Henderson allowed well-connected parents and government officials to evade lottery rules.

“I wish I could go back and look up and talk to as many people as I could about the challenge I was facing,” Wilson, who spent the weekend apologizing to council members, said in an interview Monday. “I failed miserably. It wasn’t a mistake out of anything other than trying to ensure that my daughter’s well-being was taken care of.”

Parents and council members quickly rallied behind the mayor’s decision, saying the chancellor cheated a system that D.C. families struggle to navigate.

Kerry-Ann Elliott, a Brookland resident who lives in the same high school district as Wilson’s daughter, said she opted to send her child to a Catholic school because she couldn’t find a suitable public school — and plans to keep him there through high school.

“If we had the option to go to Wilson versus Dunbar, which is our assigned school, we would love for him to go there; we would prefer to not have to pay,” Elliott said. “D.C. has that reputation of cronyism, and this definitely sent the message you can bypass those rules if you know the right people.”

Council Chairman Phil Mendelson (D) said he hopes the mayor’s decision allows the city to move forward.

“It’s clear that the public has lost confidence in the school system, and the District has been consumed with this controversy for days,” Mendelson said. “We need to get back to educating.”